Apparatus for making a one-piece, washable and sterilizable plastic shoe

ABSTRACT

A one-piece, washable and sterilizable plastic shoe comprising a lower part with a top on which the foot bears and a bottom enveloping an outsole and a heel, and an upper part having ventilating openings in a substantially vertical lateral area, these openings having upper and lower outer boundary edges that are lower, respectively, than the corresponding upper and lower inner boundary edges thereof. The method for producing such a plastic shoe includes the steps of introducing mouldable plastic into a mould comprising top and bottom halves with a shoe last therebetween and simultaneously forming the lateral ventilating openings by means of spaced pins extending between the bottom-half mould and the last. The apparatus for producing the shoe comprises a mould having top and bottom halves with a shoe last therebetween and a plurality of pins extending from the bottom-half mould into removeable engagement with the shoe last. The pins are shaped and oriented to provide the desired configuration to the ventilating openings.

This application is a division of application Ser. No. 171,666, filedJuly 24, 1980.

The present invention relates to a one-piece, washable and sterilizableplastic shoe made from a robust, elastic plastic material provided withcharacteristically shaped and arranged ventilating openings, as well asto a method and to an apparatus for producing such a shoe.

Shoes made using plastic have long been known, whereby some are madeentirely from plastic, whilst others only have certain parts, e.g. theupper or lower parts, front cap or sole made from plastic. Such shoesare more particularly used for special purposes, for example as beach,bathing and sports shoes and the like, but also are available asstandard working or walking shoes.

These known, wholly or partly plastic shoes are generally onlymanufacturable by means of relatively complicated processes and aretherefore relatively expensive. However, the wearing characteristics ofsuch shoes are also not always satisfactory, particularly with regard tothe requirements for a firm, but still comfortable fit, the slipping orsliding resistance, the pliability and elasticity as well as inparticular the completely satisfactory ventilation of the shoe.

Numerous attempts have been made to obviate these and otherdisadvantages of plastic shoes.

Thus, e.g. West German Offenlegungsschrift No. 2,238,811 describes acomplete foam moulded shoe with an instep in which the sole and upperare produced completely mechanically and separately by a foam mouldingprocess using polystyrene or polypropylene or plastic combinations. Bothparts must subsequently be durably joined together in some suitable way.

Although this shoe is much lighter than similarly shaped conventionalshoes, it has considerable deficiencies both as regards the manufactureand use. Manufacture is relatively complicated, because it is necessaryto separately produce the upper and lower parts of the shoe, after whichthey are joined together and finally must be provided with ventilatingopenings so that the shoe is provided with a certain ventilation.Further operations involve the fitting of the outsole and the heel and,in order to improve the wearing characteristics, a cushion or pad on theinside of the upper. However, despite the ventilating openings, the shoeis too hot when worn and in addition its elasticity when walking isinadequate.

In addition, a washable and disinfectable shoe is known which is mainlyintended for use in hospitals. It comprises a clog-like shoe body inwhich the upper and lower parts are combined. This shoe body is madefrom polyurethane with ventilating openings in the side portionsthereof. A profiled, slip-proof outsole and a correspondingly finishedheel are fixed to the bottom of the shoe body. The shoe body can only beused by inserting an instep raiser, which is made from polyurethane andconductively connected with an antistatic device of the shoe body bymeans of a metal gauze placed in a rectangular recess in the centre ofthe sole. Thus, the complete shoe comprises at least three to fourjoined parts (sole, heel, shoe body and instep raiser) and has verycomplicated antistatic means. Therefore, the labour costs involved inits manufacture are high, making the shoe correspondingly expensive.

Shoes made wholly or partly from plastic materials generally have thedisadvantage that when worn unpleasant localizations of heat can form onthe feet due to the thermal insulation of plastics leading to the knownunpleasant consequences.

Attempts have therefore been made to obviate this problem by providingknown plastic shoes laterally or at the top with ventilating openingshaving different configurations and sizes. However, the hitherto knownsolutions have only been partly satisfactory, because despite theventilating openings, the localizations of heat are frequency notremoved to the necessary extent or, if there are too many perforationsin the upper part of the shoe, although the ventilation is adequate, thestrength and durability of said shoe upper part are inadequate. Inaddition, the provision of the plastic shoe with ventilating openingsgenerally requires additional operations which often have to be carriedout manually instead of mechanically, which leads to a notinconsiderable increase in the cost of the products.

The problem of the present invention is to provide a shoe which isentirely made from a suitable elastic plastic material, which can beeasily mass produced in a few process stages, i.e. with minimumexpenditure and which, even in the case of prolonged use, ischaracterized by pleasant wearing characteristics, including acompletely satisfactory ventilation of the foot. The shoe is washableand sterilizable and even after being treated in this way a number oftime has substantially no undesired changes, such as deformations,material damage, etc.

According to the invention, this problem is solved by a one-piece,washable and sterilizable plastic shoe made from an elastic and robustand preferably expanded plastic material, comprising a lower part with atop on which bears the foot and a bottom enveloping an outsole and aheel which is optionally offset therefrom, as well as an upper partextending onto the lower part, forming a cavity for receiving the toes,ball and metatarsus and having ventilating openings, characterized inthat ventilating openings are provided in the substantially verticallateral area of the upper part of the shoe spaced from one another overthe outsole edge and the outer boundary edges thereof are lower than thecorresponding inner boundary edges.

The shoe according to the invention is preferably made from expandedpolyurethane. This material has numerous advantages characteristics forthe usability of a shoe, such as excellent strength and elasticity, gooddeformability, almost complete indestructibility and good thermalinsulation. Polyurethane also has the advantage that shoes made fromthis material can be easily washed and sterilized numerous times,without any risk of the shoes losing their shape, shrinking, cracking,becoming brittle or suffering any other type of material damage as aresult of this treatment. The shoes according to the invention cantherefore be used with particular advantage where high demands are madeon hygiene, e.g. in hospitals, food processing plants such as dairies,breweries, abattoirs, as well as in industrial kitchens, factoriesproducing pharmaceutical products, microbiological laboratories, etc.

The shoe according to the invention offers an effective, but simplesolution of the aforementioned ventilation problems.

According to the invention, the ventilating openings are arranged insuch a way that they ensure an optimum ventilation of the shoe, withoutsignificantly impairing the strength and durability thereof.

The formation and configuration of the ventilating openings according tothe invention also have the advantage that the already good elasticityof the shoe is further increased and therefore despite the large numberof ventilating openings provided, the protective function of the shoe isnot significantly reduced due to its characteristic construction, apartfrom the fact that it is not water-tight, which is naturally the casewith all shoes having a perforated surface.

The shoes according to the invention also have the great advantage thatthey can be manufactured in one operation and in one piece by mouldingor injection moulding of the plastic material which is in the fluidstate in a closed mould comprising a last, a bottom-half mould and atop-half mould and including the ventilating openings which, accordingto the invention, are formed in such a way that they do not impede themovements connected with the closing and opening of the upper and lowermould halves after moulding or injection moulding and also cause nodamage or premature wear to the moulds. Thus, apart from the subsequentprocessing which is to a greater or lesser extent necessary with allmoulded articles, no further time-consuming and labour-intensiveprocessing stages are necessary, which provides a considerable costsaving compared with similar known products.

An optimum frictionless removal of the shoe from the mould or injectionmould, particularly from the bottom-half mould is possible withoutdifficulty according to the invention even with the pins in the latter,said pins forming ventilating openings shaped and arranged in accordancewith the invention. It is obvious that mould removal without impairingor even destroying the shoe is not possible if during removal, the pinsare moved in a direction which is at right angles or approximately atright angles to the longitudinal axis of the pins. To permit the pins tobe removed without difficulty from the shoe, following moulding orinjection moulding and hardening of the shoe, they must be arranged andshaped in a unique way so that they can form the desired ventilatingopenings. This means that the connecting sides of the ventilatingopenings between the outer and the corresponding inner boundary edges,and consequently also the corresponding side walls of the pins, mustform an angle α below 90° with the normal line of the shoe which isperpendicular on the horizontal opening plane of the mould. It has beenfound that mould removal can be carried out particularly easily andsmoothly if the connecting sides of the ventilating openings between theouter boundary edges and the corresponding boundary edges form an angleα between 0° and 30°, preferably between 5° and 15° with the shoe normalline perpendicular to the horizontal opening plane of the mould.

The ventilating openings provided in spaced manner in the verticallateral area of the upper part of the shoe over the edge of the sole canhave various configurations. For example, the outer edges bounding theventilating openings can assume different positions relative to oneanother. According to an appropriate embodiment, the upper and lowerouter boundary edges of a ventilating opening are in a plane at rightangles to the horizontal. According to a further preferred embodiment,the upper outer boundary edge is located further to the outside than thelower outer boundary edge, so that for the same good ventilating action,the protective action of the upper part, particularly against liquidstriking from above, is increased.

The inner boundary edges of the ventilating openings are in orapproximately in a plane at right angles to the horizontal in the caseof substantially vertically directed side wall of the shoe. It has beenfound that a particularly advantageous ventilating action can beobtained if the lower inner boundary edge, relative to a plane which isat right angles to the horizontal, is positioned further inwards thanthe upper inner boundary edge. As a result, the edge of the top of thefoot support is cut somewhat in the vicinity of the ventilating openingswhich provides a better ventilation guidance, without the function ofthe foot support being impaired.

According to another advantageous embodiment of the inventive shoe, theventilating openings in the indicated lateral area are providedall-round the front upper part of the shoe in at least one row, startingin the vicinity of the heel on one side and ending in the vicinity ofthe heel on the other side, it being optionally possible to interruptthe row in the front shoe cap area.

To facilitate removal from the mould, it is also advantageous to shapethe ventilating openings in such a way that they taper conically fromthe outside to the inside.

The ventilating openings provided in accordance with the invention canbe in the most varied forms in accordance with requirements and fashion.Advantageously, configurations are rectangular, square, circular or ovalventilating openings.

According to a further advantageous development of the shoe according tothe invention, additional ventilating openings are provided in thesubstantially horizontal area of the front upper part of the shoe.Although the ventilating openings provided according to the invention inthe area of the sole edge and the upper part directly adjacent theretoin themselves ensure a good ventilation due to their favourablepositioning with respect to the foot in the shoe, provided that they arepresent in adequate numbers and size, it may in some cases be desirableto assist this ventilation by additional ventilating openings on thesubstantially horizontal upper part of the shoe. However, the diameterof these additional openings must not exceed a certain value. It hasbeen found that an additional ventilation of the shoe withoutsignificantly impairing the protective function of the upper part isensured if the additional ventilating openings have a maximum diameterof 3 mm.

The additional ventilating openings can be given the most varied shapes,e.g. square or circular and can be provided on the front upper part ofthe shoe in the most varied regular or irregular arrangements, so thate.g. when regularly arranged, patterns are obtained which at the sametime give the shoe a particularly attractive appearance.

Obviously, the shoe according to the invention can be provided withfurther useful characteristics and features. Thus, the shoe can be givenan antistatic finish or can be suitably coloured by adding suitablyacting agents to the plastic, preferably the polyurethane prior tomoulding or injection moulding. In addition, the sole and heel areas ofthe shoe are appropriately produced in such a way that they areslip-proof. In the most simple manner, this can be brought about by theoutsole and heel surfaces having a slip-proof, profile-like surfacearea.

The shape and construction of the shoe according to the invention caneasily be modified without passing beyond the inventive principle. Forexample, the outer surfaces of the shoe can be subject to any desiredand technically possible development. Thus, the outer surfaces of theupper part and heel can be made smooth or provided with a pattern, e.g.they can be grained, provided with a wood grain-like pattern, etc.Obviously, the shoe according to the invention can be manufactured inany desired size and, if desired, can be given any random colouring.

The invention also relates to a method for producing a one-piece,washable and sterilizable plastic shoe by moulding or injectionmoulding. The method according to the invention is characterized in thatan adequate quantity of a mouldable or injection mouldable, optionallyfoamable plastic material is introduced in a fluid state and at anappropriate temperature into an optionally heatable and/or coolablemould or injection mould comprising the top-half mould and a bottom-halfmould and a correspondingly adapted last and the shoe is moulded in onepiece, the lateral ventilating openings on the shoe being shaped in thelast during the moulding process by suitably shaped and arranged pins inthe bottom-half mould and optionally corresponding recesses in which thepins can engage, the introduced plastic material optionally being leftin the mould for an adequate time for complete foaming to take place andfor the foaming to harden, whereby after the plastic material hashardened the mould is opened and the plastic shoe is removed therefrom.

The plastic material used is optionally a foamable or expandablepolyurethane, the isocyanate component and the dihydroxy or polyhydroxycomponent, optionally together with foaming agents and otherconventional additives being intensely mixed together in a suitablemixer just prior to the moulding or injection moulding of the shoe.

The isocyanate component can be known, commercially available,moderately viscous prepolymers which are liquid at room temperature orslightly elevated temperatures. They are prepared by per se knownmethods by polyesters or polyethers with excessive quantities ofdiisocyanate. The dihydroxy or polyhydroxy component mainly comprisesglycols and essentially serves as a chain extender for producingpolyurethane s with the desired elastomeric characteristics. Thepolyurethane is preferably used in expanded form, 0.1 to 0.4% by water,based on the isocyanate-free component quantity is added as the foamingagent to said component.

If desired, the foaming agent can also be constituted by inert,low-boiling liquids such as trichlorofluoromethane, optionally combinedwith a small amount of water.

The moulding or injection moulding of the shoe appropriately takes placeat a temperature at which the plastic material used is fluid, preferablyin the range approximately 10° to 60° C.

The method can be performed in per se known moulds for producingone-piece plastic shoes suitable for moulding or injection mouldingfluid plastic material. Such moulds generally comprise the bottom-halfmould, the top-half mould and correspondingly adapted last, whereby saidmembers are normally movable relative to one another and generally thetop-half mould and last are raised from the bottom-half mould and can bemoved about a horizontal axis. Advantageously, a pair of shoes issimultaneously produced in paired moulds. Twelve to twenty-four suchpaired moulds are normally arranged in a circle or so-called carousel.However, the method can also be performed by other known mouldconfigurations.

The moulded or injection moulded shoe provided with the lateralventilating openings is advantageously removed from the mould in such away that initially the top-half mould is moved by a large distancetherefore and the last by a smaller distance in the upwards directionabout a horizontal axis. The shoe is drawn out of the bottom-half mouldwith the pins for forming the lateral ventilating openings and isdetached from the top-half mould. The shoe is then removed from thelast.

The invention also relates to an apparatus for producing a one-piece,washable and sterilizable plastic shoe, which essentially comprises anoptionally heatable and/or coolable mould or injection mould with abottom-half mould, a movable top-half mould and an optionally movable,correspondingly adapted last. The apparatus according to the inventionis characterized in that in the bottom-half mould pins are provided,which are arranged and shaped in such a way that they form lateralventilating openings on the shoe, whose outer boundary edges are lowerthan the corresponding inner boundary edges and which in thesubstantially vertical lateral area of the upper part of the shoe arespaced from one another over the outsole edge and that the last isoptionally provided with corresponding recesses in which the pins canengage.

This apparatus is eminently suitable for producing a one-piece plasticshoe according to the invention, the pins provided in the bottom-halfmould being shaped and arranged in such a way that on the one hand theyreliably form the characteristic lateral ventilating openings in theshoe and on the other permit a rapid and substantialy frictionless andremoval of the shoe from the mould. According to a particularlypreferred embodiment, the pins are arranged and shaped in such a waythat they form lateral ventilating openings on the shoe and whoseconnecting sides between the outer boundary edges and the correspondinginner boundary edges form an angle between 0° and 30°, preferablybetween 5° and 15° with the nornal line of the shoe positionedperpendicularly on the horizontal opening plane of the mould.

The pins provided in the bottom-half mould can have differentconfigurations as a function of the different embodiments of the lateralventilating openings. Thus, according to an advantageous embodiment,they are shaped in such a way that they form ventilating openings on theshoe, whose upper and lower outer boundary edges are located in oneplane at right angles to the horizontal of the shoe. According toanother preferred embodiment, the pins are shaped in such a way thatthey form ventilating openings on the shoe in which the upper outerboundary edge is located further outwards than the lower outer boundaryedge. Finally, the pins can also be shaped in such a way that they formventilating openings on the shoe, whose lower inner boundary edges arepositioned further inwards than the corresponding upper inner boundaryedges. In this embodiment, particularly effective ventilating openingsare formed by the pins.

In the bottom-half mould, the pins can be arranged in one or more rows,so that in the substantially vertical lateral area, they form one ormore rows of all-round ventilating openings, which start in the vicinityof the heel on one side of the shoe and end in the vicinity of the heelon the other side thereof and optionally the front shoe cap can berecessed.

If desired, the pins can have a different cross-sectional shape.Appropriately, these pins have a rectangular, square, circular or ovalcross-section.

The construction and shape of the pins in the bottom-half mouldconsiderably influence the quality of the ventilating openings in theshoe according to the invention. They also influence the possibility ofremoving the shoe from the mould. Independently of other configurations,preference is given to pins which taper conically towards the pin end,which considerably facilitates the removal from the mould of thehardened plastic shoe.

The invention is described in greater detail hereinafter relative to thedrawings, which form a part hereof and wherein

FIG. 1 is a perspective view of an embodiment of a shoe according to theinvention.

FIG. 2 is a cross-sectional through the front part of the shoe of FIG. 1at the section line designated A--A.

FIG. 3 is an enlarged cutaway portion B of FIG. 2 with a firstembodiment of the ventilating openings according to the invention.

FIG. 4 is another enlarged cutaway portion B from FIG. 2 with anotherembodiment of the ventilating openings according to the invention.

FIG. 5 is another enlarged cutaway portion B from FIG. 2 with aparticularly preferred embodiment of the ventilating openings accordingto the invention.

FIG. 6 is a further embodiment of the shoe according to the inventionwith additional ventilating openings on the horizontal surface of thefront part of the shoe.

FIG. 7 is a cross-sectional through an apparatus according to theinvention with top and bottom-half moulds with pins for the lateralventilating openings and fitted last, the right-hand half of the drawingshowing one embodiment and the left-hand half another embodiment.

FIG. 8 is a cross-section through another embodiment of the apparatusaccording to the invention.

In FIG. 1, the complete shoe according to the invention is designated 1,its lower part 2 and its upper part 3. The substantially vertical sideor lateral area 5 of upper part 3 in which the ventilating openings 6according to the invention are provided is bounded approximately by theline 4 and also by the outsole edge 10.

In the represented embodiment, the outsole and heel are offset withrespect to one another. Obviously, other embodiments are possible inwhich the outsole and heel extend into one another in a more or lessdefinite manner. Upper part 3 is linked with lower part 2 and forms acavity offering adequate space for the toes with the ball and metatarsusand which protectively surrounds them. The upper part terminates in aninsertion opening 7 which leaves the heel free and which enables thefoot to slip easily into and out of the shoe. If desired, the rear shoecap 8, which is only intimated in the present embodiment, can be raisedto such an extent that it surrounds and protects the heel, or other perse known supports can be provided for the heel.

In the case of the embodiment of FIG. 2, the ventilating openings 6according to the invention in the upper part area 5 are arranged ingiven spacings in a row around the front part of the shoe, the rowstarting in the vicinity of the shoe heel and being interrupted in thevicinity of the front shoe cap 9. As is not apparent from FIG. 1, it iscorrespondingly continued on the other side of the shoe and terminatesin the vicinity of the heel. Instead of a single row of ventilatingopenings, two or more such rows can be provided in the substantiallyvertical area 5 of the upper part. These rows are parallel to oneanother and the ventilating openings of adjacent rows are preferablydisplaced relative to one another, i.e. staggered. Obviously,ventilating openings can also be provided in the vincinity of the frontshoe cap 9.

Webs 11, which connect the upper part 3 to the sole edge 10, are locatedbetween adjacent ventilating openings 6.

A section along the line A--A in FIG. 1 through the front part of theshoe is shown in FIG. 2. The cross-section shows the upper part 3enveloping the front foot space with the laterally provided ventilatingopenings 6. FIG. 3 shows in detailed form how such a ventilating opening6 is constructed in area B of FIG. 2. Ventilating opening 6 is locatedin the vertical side or lateral area 5 of upper part 3 and is bounded byouter boundary edges 12 and 13 and inner boundary edges 14 and 15. Theouter boundary edges 12 and 13 are positioned lower than thecorresponding inner boundary edges 14 and 15. As can be gathered fromFIG. 3, the upper outer boundary edge 12 with the lower outer boundaryedge 13 and the upper inner boundary edge 14 with the lower innerboundary edge 15 are respectively approximately in one plane N at rightangles to the horizontal H. Hereinafter, this plane N is called the"shoe normal". The cross-section of FIG. 3 shows a constant diameter forventilating opening 6. According to further developments of theinvention, the ventilating openings can also preferably conically taperinwards.

FIG. 3 also shows that the connecting side located between the outerboundary edge 12 or 13 and the corresponding inner boundary edge 14 or15 forms an angle α with the shoe normal N which is perpendicularlypositioned on the horizontal plane H, which generally at the same timeconstitutes the opening plane for the mould. In order that the pinsprojecting into the moulded shoe and which form the lateral ventilatingopening 6 do not prevent or make unnecessarily difficult the removal ofthe shoe from the mould, the angle α must be smaller than 90°. Mouldremoval takes place particularly simply and smoothly with an angle α of0° to 30°, preferably 5° to 15°.

A further preferred embodiment of the ventilating openings is shown inFIG. 4. It differs from that of FIG. 3 by the position of the upper andlower boundary edges 12a, 14a and 13a, 15a with respect to one another.It is clear that the upper outer boundary edge 12a is locatd furtheroutwards than the lower outer boundary edge 13a. As shown in FIG. 4,such a position is obtained if in the vicinity of the ventilatingopenings, side wall 5a bulges out in convex manner in the vicinity ofthe ventilating openings instead of being perpendicular to plane H. FIG.4 also shows as a particularly preferred embodiment, a connecting sidelocated between the lower boundary edges 13a and 15a which is positionedin such a way that it intersects the foot support surface 16 in thevicinity of ventilating opening 6a. This leads to a position in whichthe lower inner boundary edge 15a is positioned further inwards than theupper inner boundary edge 14a, so that when the shoe is being worn,ventilating opening 6a is partly located laterally under the foot.Ventilating openings in this position have proved to be particularlyeffective.

FIG. 5 shows another embodiment of the ventilating openings where, as inFIG. 4, the lower outer boundary edge 13b is located on the outsole edge10, but the ventilating opening 6b tapers conically inwards from edges12b and 13b to edges 14b and 15b.

As a result of the construction of the ventilating openings according tothe invention and for which only a few preferred embodiments have beenshown in exemplified manner in FIGS. 1 to 5, it is readily possible toremove the pins connected to the bottom-half mould from the ventilatingopenings after the injection moulded shoe has cooled. As a result of theconstruction and arrangement of the ventilating openings according tothe invention, the outsole surface of the shoe is substantially notreduced. As is apparent from FIGS. 3 and 4, the construction of theventilating openings 6 and 6a according to the invention prevents e.g.liquid dropping from above onto the shoe from passing through openings 6and 6a into the interior of the shoe. Between in each case two adjacentventilating openings, there is a web 11 (indicated by two solid lines inFIGS. 3 to 5) forming a connection between upper part 3 and sole edge10.

FIG. 6 shows another embodiment of the shoe according to the inventionin which additional circular ventilating openings are arranged in theform of rows on the substantially horizontal top area of the front upperpart. An additional ventilating slot is provided in the front shoe capapproximately level with the ventilating openings provided on the sidesaccording to the invention.

FIGS. 7 and 8 show apparatuses according to the invention for producinga plastic shoe with the characteristic lateral ventilating openingsaccording to the invention in cross-sectional form. The apparatuscomprises the top-half mould 20, the bottom-half mould 21 and last 22.Pins 23 are provided on the bottom-half mould 21 and form the lateralventilating openings on the shoe. The left-hand half of FIG. 7 shows anembodiment in which pin 23 is constructed in such a way that it forms aventilating opening whose upper outer boundary edge 12a, as seen in FIG.4, is positioned further outwards than the lower outer boundary edge 13alocated directly on the outsole edge 10. The connecting side between thelower outer and lower inner boundary edge intersects the edge of thefoot support surface 16 in the vicinity of the ventilating opening, sothat the latter projects to a small extent into the foot supportsurface. Last 22 is provided with a corresponding recess 24 in whichengages pin 23. The cross-section also shows that pin 23 tapers towardsthe pin end, so that as a result ventilating openings are formed whichtaper conically from the outside to the inside.

The right-hand half of FIG. 7 shows a further embodiment in which pin23a is constructed in such a way that it forms a ventilating opening inwhich the upper and lower outer boundary edges are in one plane at rightangles to the horizontal opening plane H. The connecting sides aresubstantially parallel to one another, the lower outer boundary edgebeing positioned above the outsole edge. A recess 24a adapted to pin 23ais provided in lasts 22.

FIG. 8 shows another embodiment of the apparatus according to theinvention in which the pin 23b is directly bounded by the plane passingthrough the inner boundary edges 14 and 15, so that last 22 has norecess for pin 23.

The embodiments of the invention described hereinbefore are intended tobe of a non-limitative exemplified nature and obviously numerousvariants are possible thereto which also utilize the inventive concept.Thus, for example, it is also possible to produce the lower partprovided with the ventilating opening according to the invention, theoutsole and the heel separately from the other part of the shoe. Theupper part of the shoe can then also be from a different material to thelower part, e.g. a different plastic, leather, canvas, etc. The upperand lower parts are then interconnected at the same time as producingthe lower part or after producing the latter. These and similarembodiments obviously fall within the scope of the invention.

As seen in FIG. 8, the top of the base of pin 23b on bottom-half mould21 is lower than the top of the distal end of pin 23b in engagement withthe last 22. Similarly, the bottom of the base of pin 23b on bottom-halfmould 21 is lower than the bottom of the distal end of pin 23b inengagement with the last 22. In addition, the side walls of the pin 23bbetween the base and distal end of the pin forms an angle α which isless than 90° with the normal line N of the shoe, the normal line beingperpendicular to the horizontal opening plane H of the mould.Advantageously, the angle α is between 0° and 30°, and preferablybetween 5° and 15°.

We claim:
 1. An apparatus for producing a one-piece, washable andsterilizable plastic shoe comprising:a mould with a bottom-half mould,and a moveable top-half mould, and a correspondingly adapted shoe lastlocated therebetween to form an entire shoe, said bottom-half mouldhaving pins extending therefrom which are upwardly and inwardly directedfrom said bottom-half mould towards and into engagement with said last,and spaced along said bottom-half mould so that they form lateralventilating openings (6) on the shoe, whose outer boundary edges (12,13) are lower than the corresponding inner boundary edges (14, 15) andwhich in the substantially vertical lateral area (5) of the upper partof the shoe are spaced from one another over the outsole edge (10). 2.An apparatus according to claim 1, characterized in that the last isprovided with corresponding recesses in which the pins can engage.
 3. Anapparatus according to claim 1, characterized in that the pins in thebottom-half mould are arranged and shaped in such a way that they formlateral ventilating openings (6) of the shoe, whose connecting sidesbetween the outer boundary edges (12, 13) and the corresponding innerboundary edges (14, 15) form an angle between 0° and 30° with the normalline of the shoe perpendicular to the horizontal opening plane of themould.
 4. An apparatus according to claim 1, characterized in that saidangle is between 5° and 15°.
 5. An apparatus according to claim 1,characterized in that the pins connected to the bottom-half mould areshaped in such a way that they form ventilating openings (6) on theshoe, whose upper and lower outer boundary edges (12, 13) are in oneplane at right angles to the horizontal.
 6. An apparatus according toclaim 1, characterized in that the pins connected to the bottom-halfmould are shaped in such a way that they form ventilating openings onshoe (6), the upper outer boundary edge (12) being further to theoutside than the lower outer boundary edge (13).
 7. An apparatusaccording to claim 1, characterized in that the pins are shaped in sucha way that they form ventilating openings (6) on the shoe, whose lowerinner boundary edges (15) are positioned further inwards than thecorresponding inner boundary edges (14).
 8. An apparatus according toclaim 1, characterized in that the pins connected to the bottom-halfmould are arranged in such a way that in the specified, substantiallyvertical lateral area (5) of the shoe they form at least one row ofall-round, ventilating openings (6) beginning in the vicinity of theheel on one side of the shoe and ending in the vicinity of the heel onthe other side of the shoe.
 9. An apparatus according to claim 1,characterized in that the pins have a rectangular cross-section.
 10. Anapparatus according to claim 1, characterized in that the pins have acircular cross-section.
 11. An apparatus according to claim 1,characterized in that the pins have an oval cross-section.
 12. Anapparatus according to claim 1, characterized in that the pins taperconically towards the pin end.
 13. An apparatus for producing aone-piece, washable and sterilizable plastic shoe comprising:a mouldhaving a bottom-half mould, and a moveable top-half mould, and a shoelast located therebetween to form an entire shoe, said bottom-half mouldhaving spaced pins extending therefrom into engagement with said last toform lateral ventilating openings in the shoe, said pins being upwardlyand inwardly directed from said bottom-half mould towards said last,each of said pins having the top of the base thereof extending from saidbottom-half mould lower than the top of the distal end thereof inengagement with said last and having the bottom of the base thereofextending from said bottom-half mould lower than the bottom of thedistal end thereof in engagement with said last.
 14. An apparatusaccording to claim 13, characterized in thatthe top and bottom sidewalls of each of said pins between the base and distal end thereof formsan angle which is less than 90° with the normal line of said shoe. 15.An apparatus according to claim 14, characterized in thatsaid angle isbetween 0° and 30°.
 16. An apparatus according to claim 14,characterized in thatsaid angle is between 5° and 15°.